o-TOLUIDINE CAS N°: 95-53-4 - UNEP Chemicals

OECD SIDS o-TOLUIDINE
prepared from o-toluidine but do not contain relevant o-toluidine levels (< 0.1 %) (Swiss Product
Register, 2004).
An OSHA report from 1982 states (cited according to NTP, 2003): “Consumer exposure to o-toluidine
may possibly occur from residues present in commercial dyes used on textiles.” (NTP, 2003).
In the EU, the use of azo dyes releasing o-toluidine on degradation, is not permitted for textiles and
other consumer articles (EU, 1976; 2002; 2003). The same conclusion has been drawn by the IARC
(2000).
Environmental tobacco smoke contains significant levels of several aromatic amines including
o-toluidine (2 - 4 µg o-toluidine/cigarette) (Luceri et al., 1993). Tobacco leaves (Irvine and
Saxby, 1969; IARC, 2000) and tobacco smoke (Pailer, Huebsch and Kuhn, 1966; Neurath, 1969;
Schmeltz and Hoffmann, 1977) contain significant amounts of o-toluidine. Tobacco smoke
contaminates the air of virtually all inhabited environments (cf. Chapter 2.2.8). Since several ringsubstituted
aromatic amines are most likely formed by pyrolysis (Neurath, 1969), generally, smoke
derived from nitrogen-containing fuels may contain o-toluidine and contaminate consumer products
including food (cf. Chapter 2.2.8).
In human milk from 7 smokers and 24 non-smokers, there were < 0.01 to 0.26 ppb (ng/g)
o-toluidine, with an average of 0.04 ppb (for comparison, the level of aniline was 0.36 ppb and of
N-methylaniline 0.55 ppb). No significant differences between the two groups were observed. None
of the women reported occupational exposure to aromatic amines. The authors explain their
observation with the occurrence of aromatic amines in tobacco smoke, fresh vegetables and the
aroma of black tea (DeBruin, Pawliszyn and Josephy, 1999).
In the general population (200 adults from Western Germany), the level of o-toluidine in urine was
0.44 µg/l (median, 0 - 12 µg/l) (Weiss et al., 2000). Similar values were observed by Riffelmann et
al. (1995), who also found significant increases in the o-toluidine level in urine of smokers (mean
1.7 µg/l, n = 8), compared to urine of non-smokers (0.0 µg/l, detection limit 0.01 µg/l, n = 8).
In a study on hemoglobin adducts of aromatic amines in children from three different-sized
Bavarian towns, Richter et al. (2001) found no influence of exposure to environmental tobacco
smoke (determined by interview) on o-toluidine hemoglobin adduct levels, but observed the highest
adduct levels in the largest town. In contrast, Lewalter and Neumann (1996) report that the
hemoglobin adduct background level of toluidine (no isomer specified) is 1 - 10 µg/l for the general
population due to tobacco smoke.
Stillwell, Bryant and Wishnok (1987) found significant differences between smokers (n = 12) and
non-smokers (n = 10). The o-toluidine-hemoglobin-adduct level was tripled in smokers (0.10 ng/g
hemoglobin), compared to non-smokers (0.034 ng/g hemoglobin). Skipper, Bryant and
Tannenbaum (1988) confirmed these results with smokers and non-smokers from Turin (Italy) and
Boston (USA). In the Boston cohort, the o-toluidine-hemoglobin-adduct level was 0.25 - 0.45 ng/g
hemoglobin for different groups of smokers, and 0.09 ng/g hemoglobin for non-smokers. In the
Turin cohort, the o-toluidine-hemoglobin-adduct level was 0.29 ng/g hemoglobin in smokers, and
0.17 ng/g hemoglobin in non-smokers. Significant differences between smokers and non-smokers
were also obtained by Bryant et al. (1988) for slightly different cohorts from Turin. In these cohorts,
the o-toluidine-hemoglobin-adduct level was 0.31 ng/g hemoglobin in smokers, and 0.19 ng/g
hemoglobin in non-smokers.
These data indicate that consumers are exposed to o-toluidine in tobacco smoke (including
environmental tocacco smoke) and some foodstuffs. Tobacco smoke is the predominant source of
o-toluidine in humans.
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